[ray_mcavoy]

It could be a failed turn signal switch.

You can unplug it at the long flat "harmonica" connector on the steering column under the dash for testing without having to tear the column apart.

With the switch unplugged, you can use an ohmmeter to test for continuity between the various wires of the switch. In the "left turn" position, there should be continuity between the purple wire and the light blue wire. As well as continuity between the purple wire and the yellow wire. Similarly, in the "right turn" position there should be continuity between the purple, dark blue, and dark green wires.

Also with the switch unplugged, you can temporarily install jumper wires on the truck half of the wiring connector to simulate the functions of the switch. That'll let you know if the problem is in the switch or somewhere else. Jumpering the purple wire to both the light blue & yellow wires should make the left turn signals flash. Similarly, jumpering the purple wire to both the dark blue & dark green wires should make the right turn signals flash.